[AMDGPU] Move DWARF proposal to separate file

- Move DWARF proposal for heterogeneous debugging to a separate file.
- Add references.

Differential Revision: https://reviews.llvm.org/D70523
diff --git a/llvm/docs/UserGuides.rst b/llvm/docs/UserGuides.rst
index 5673ae6..af0d5ad 100644
--- a/llvm/docs/UserGuides.rst
+++ b/llvm/docs/UserGuides.rst
@@ -192,4 +192,8 @@
    This document describes using the NVPTX backend to compile GPU kernels.

 

 :doc:`AMDGPUUsage`

-   This document describes using the AMDGPU backend to compile GPU kernels.
\ No newline at end of file
+   This document describes using the AMDGPU backend to compile GPU kernels.

+

+:doc:`AMDGPUDwarfProposalForHeterogeneousDebugging`

+   This document describes a DWARF proposal to support heterogeneous debugging

+   for targets such as the AMDGPU backend.
\ No newline at end of file